-LRB- CNN -RRB- -- Rangers scored three second-half goals to beat Celtic 4-2 in Glasgow 's Old Firm Derby Sunday and go four points clear in the Scottish Premier League .

In-form Steven Naismith fired Rangers ahead with a thumping strike after 22nd minutes but Celtic were quick to level through Gary Hooper 's well-worked goal 12 minutes later .

Celtic took the lead just before halftime as Rangers goalkeeper Allan McGregor allowed a weak shot from Moroccan Badr El Kaddouri to elude his grasp and trickle into the net .

But Nikica Jelavic headed Rangers level seven minutes after the interval and they were ahead when Kyle Lafferty converted after 67 minutes .

Mulgrew , who was fortunate to escape with just a yellow card for his first half challenge , then saw red in the 75th minute and Naismith took advantage against 10 men to score the fourth and his second in injury time .

`` I did n't think there was an awful lot between the teams in the first-half . I 'm not sure we deserved to go in 2-1 down but that 's what we were faced with , '' Rangers manager Ally McCoist told Sky Sports .

`` We asked the boys for a reaction in the second-half and boy did we get it . ''

Celtic manager Neil Lennon was disappointed by his team 's second half display : `` We did n't compete and it was almost as if the players had gone out in the second-half thinking the game was won , '' he said .

Matches between the two giants of Scottish football usually prove crucial in the domestic title race and the victory left Rangers on 19 points after seven games , with Celtic on 15 in second .

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Rangers score three second half goals to beat Celtic in Glasgow 's Old Firm Derby

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Steven Naismith on target in each half for Rangers who go four points clear at top in Scotland

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Celtic have Charlie Mulgrew sent off in the second half for second bookable foul

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Old Firm Derby is one of the most hotly-contested in world football